Radiation Exposure and Image Quality in X-Ray Diagnostic Radiology

Radiation Exposure and Image Quality in X-Ray Diagnostic Radiology Horst Aichinger • Joachim Dierker Sigrid Joite-Barfuß • Manfred S€abel Radiation...
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Radiation Exposure and Image Quality in X-Ray Diagnostic Radiology

Horst Aichinger • Joachim Dierker Sigrid Joite-Barfuß • Manfred S€abel

Radiation Exposure and Image Quality in X-Ray Diagnostic Radiology Physical Principles and Clinical Applications Second Edition

Authors Dr. Horst Aichinger Unterfarrnbacher Str. 32 90766 Fu¨rth Germany [email protected] Dipl. Phys. Sigrid Joite-Barfuß Friedhofstr. 4a 91058 Erlangen Germany [email protected]

Dr. Joachim Dierker Hegenigstr. 56 91056 Erlangen Germany [email protected] Prof. Dr. Manfred Sa¨bel Universit€atsklinikum Erlangen Radiologisches Institut Maximiliansplatz 1 91054 Erlangen Germany [email protected]

ISBN 978-3-642-11240-9 e-ISBN 978-3-642-11241-6 DOI 10.1007/978-3-642-11241-6 Springer Heidelberg Dordrecht London New York Library of Congress Control Number: 2011928414 # Springer-Verlag Berlin Heidelberg 2012 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer. Violations are liable to prosecution under the German Copyright Law. The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Product liability: The publishers cannot guarantee the accuracy of any information about dosage and application contained in this book. In every individual case the user must check such information by consulting the relevant literature. Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com)

Preface to the 1st Edition

X-ray diagnostic radiology is a major world-wide activity. In Europe approximately 250 million X-ray examinations are performed annually, and in the United States of America a similar level of radiological activity is undertaken. This results in the fact that the largest contribution to radiation exposure to the population as a whole is known to be from man made radiation sources arising in the form of diagnostic X-rays (UNSCEAR 2000). It is also known that exposures vary widely, due to differences in X-ray techniques and the level of skill of the operator of the equipment. Consequently radiation protection of the patient is a major aim in modern health policy. The two basic principles of radiation protection of the patient as recommended by the International Commission on Radiological Protection (ICRP 1991) are justification of practice and optimisation of protection. Justification is the first step in radiation protection. It is generally accepted that no diagnostic exposure is justifiable without a valid clinical indication. In comparison to the associated radiation risk, every examination must result in a net benefit for the patient. Justification also implies that the necessary result cannot be achieved with other methods which would be combined with lower risks for the patient. Once a diagnostic X-ray examination has been clinically justified, the subsequent imaging process must be optimised. The optimal use of X-rays involves the interplay of three important aspects of the imaging process (CEC 1996): • The diagnostic quality of the radiological image • The radiation dose to the patient • The choice of imaging technique In respect of diagnostic radiology, the ICRP does not recommend the application of dose limits to patient irradiation but draws attention to the use of dose reference levels as an aid to optimisation of protection in medical exposure. The principles of justification and optimisation are largely translated into a legal framework by the Medical Exposure Directive (MED) 97/43/Euratom (CEC 1997). Concerning optimisation the MED states explicitly in Article 4, 1(a) that: • ‘All doses due to medical exposure for radiological purposes, except radiotherapeutic procedures, shall be kept as low as reasonably achievable consistent with obtaining the required diagnostic information, taking into account economic and social factors’. This concept is known as the ALARA principle (as low as reasonably achievable). In Article 4, 2.(a) the MED states that: • ‘Member States shall promote the establishment and the use of diagnostic reference levels for radiodiagnostic examinations’. Diagnostic reference levels are defined in Article 2 of the MED as: • ‘Dose levels in medical radiodiagnostic practices for typical examinations for groups of standard-sized patients or standard phantoms for broadly defined types of equipment. These levels are expected not to be exceeded for standard procedures when good and normal practice regarding diagnostic and technical performance is applied’. v

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Preface to the 1st Edition

The authors of this book have been engaged for a long time in the solution of problems concerning optimisation in X-ray diagnostic radiology, three of us (Aichinger, Dierker, Joite-Barfuß) as physicists in development working groups of Siemens Medical Solutions and one (S€abel) as a medical physicist in a university hospital. During this time a lot of data material have been accumulated, which could be useful for physicists and engineers in the medical radiodiagnostic industry, for medical physicists and for diagnostic radiologists working at problems of image quality, patient dose estimation and especially the establishment of diagnostic reference levels. In this connexion the publication of the MED was the trigger point for our decision to collect and publish this material. In particular the figures and tables included should enable a medical physicist to: • Calculate the scatter-free characteristic quantities of the primary radiation beam • Estimate patient doses (organ dose, effective dose) • Optimise radiographic and fluoroscopic exposure parameters in relation to the medical indication • Take into account the influence of scattered radiation on image quality and dose The data provided for the solution of these tasks are partly based on X-ray spectra, measured on diagnostic X-ray tube assemblies, and supplemented by the results of measurements on phantoms and simulation calculations. Taking into consideration that mammography screening is increasingly established X-ray mammography is treated in some detail. On the other hand, concerning computed tomography, the presentation is confined to the aspect of dose estimation. An essential reason for this is that one of our colleagues (Kalender 2000) has written an excellent book on computed tomography, which covers the aspect of image quality in detail. Our book consists of three parts: • The ‘Physical Principles’ reviews some information on radiation physics, dosimetry and X-ray diagnostic technique, which will be useful for the understanding of the figures and tables, but it is not intended to replace standard books on the physics of diagnostic radiology. • In the ‘Clinical Applications’ the material presented is applied to some clinical problems concerning radiation exposure of the patient, image quality and optimisation of imaging equipment. • The ‘Supplement’ includes all the figures and tables, which are necessary for the calculations. It is complimented by a CD-ROM that includes the most important data of the ‘Supplement’ and a lot of additional useful files. A detailed description of the contents of the different parts of the book is given in the following ‘Introduction’. In the preparation of this book we asked for and received the help of a number of wellqualified people: We are grateful to John H. Hubbell, Ph.D., from the National Institute of Standards and Technology, Gaithersburg, USA, for his support in the selection of the most upto-date photon interaction coefficients and to G.T. Barnes, Prof. Ph.D., from the University of Alabama in Birmingham, USA, for information in respect to his work about scattered radiation in mammography. Moreover we thank Tassilo v. Volkmann, Ph.D. from Kodak for the provision of the data of screen-film combinations and M.A.O. Thijssen, Ph.D. from the University Hospital in Nijmegen, Netherlands, for information about his CDRAD-phantom. Last but not least we thank I. Aichinger for her preparation of some of the figures in this book. Horst Aichinger Joachim Dierker Sigrid Joite-Barfuß Manfred S€abel

Preface to the 1st Edition

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References CEC (Commission of the European Communities) 1996. European Guidelines on Quality Criteria for Diagnostic Radiographic Images. EUR 16260 (Luxemburg: CEC) CEC (Commission of the European Communities) 1997. Council Directive 97/43/EURATOM of 30 June 1997 on health protection of individuals against the dangers of ionising radiation in relation to medical exposure, Official Journal of the European Communities, No L 180/22 ICRP (International Commission on Radiological Protection) 1991. 1990 Recommendations of the ICRP, Publication 60, Annals of the ICRP 21 No. 1–3 (New York: Pergamon Press) Kalender W A (2000) Computed Tomography. (M€ unchen: Publicis MCD) UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation) 2000. Sources and Effects of Ionizing Radiation. (New York: United Nations)

Preface to the 2nd Edition

Since the publication of the first edition in 2004 X-ray imaging has become almost completely digital in modern diagnostic radiology institutes. On the other side there are still a lot of X-ray units in operation which use film-screen combinations for radiography and image intensifiers for fluoroscopy. Therefore we have decided to leave the concerning material in the book essentially as it was. Furthermore for the full understanding of the new potentials in digital imaging, i.e. the advantages and further development possibilities but also the complexity, the knowledge of the physics in conventional imaging is of great importance. In addition the frequency of computed tomography increases still rapidly, and – because it involves larger radiation doses than most of the conventional imaging procedures – obtains growing attention also in radiation protection. Accordingly we have added to this edition some facts on the principles of CT imaging. In detail the following improvements have been carried out: • More detailed consideration of the aspects of image quality and radiation exposure in digital imaging and computed tomography • Actualisation of the cited references • Removal of obsolete text passages, figures and tables • Correction of discovered printing errors We are grateful to Elke Nekolla, Ph.D., from the German Federal Office for Radiation Protection for placing Fig. 1.1 to our disposal. Furthermore we are grateful to Dr. Helmuth Schramm from Siemens Medical Solutions for his information about the functioning of fluoroscopy when using a flat panel image receptor in modern X-ray equipments. Horst Aichinger Joachim Dierker Sigrid Joite-Barfuß Manfred S€abel

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Contents

Part I

Introduction

1

Principles of X-Ray Imaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Projection Radiography and Fluoroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Computed Tomography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3 3 5 7

2

Structure of the Book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Part II: Physical Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Part III: Clinical Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Part IV: Supplement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 CD-ROM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9 9 9 10 10 10

Part II

Physical Principles

3

Production and Measurement of X-Rays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Measuring Photon Spectra of Diagnostic X-Rays . . . . . . . . . . . . . . . . . . . . . 3.2.1 X-Ray Spectrometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.2 Measuring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.3 Corrections for Detector Influences . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.4 Preparing for Calculations with X-Ray Spectra . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13 13 17 17 18 18 19 19

4

Interaction of Photons with Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Exponential Law of Attenuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Interaction Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.1 Compton Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.2 Photoelectric Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.3 Rayleigh Scattering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Total Coefficients for Attenuation, Energy Transfer and Energy Absorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

21 21 21 22 23 25

5

Radiation Field and Dosimetric Quantities . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 General Radiation Field Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Characteristics of the Radiation Field in Projection Radiography and Fluoroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 Characteristics of the Radiation Field in Computed Tomography . . . . . . . . .

25 31 33 33 35 35

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6

7

8

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Contents

5.4 Dosimetric Quantities for the Description of Radiation Exposure . . . . . . . . . 5.5 Effect of Filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

36 37 39

Penetration of X-Rays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 Attenuation by the Patient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.1 Simulation of Attenuation by the Patient . . . . . . . . . . . . . . . . . . . . . 6.1.2 Basis of Exposure Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 Attenuation by the Patient Support and the Components of the Imaging Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.1 Patient Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.2 Anti-scatter Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.3 Ionisation Chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.4 Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 Important Differences Between Over-Table and Under-Table X-Ray Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4 Characteristics of Computed Tomography . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

41 41 42 43 46 46 47 48 48 50 51 51

Scattered Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1 Measurement of Scattered Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 Properties of Scattered Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.1 Radiography and Fluoroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.2 Mammography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.3 Computed Tomography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3 Techniques in Radiography and Fluoroscopy to Reduce Scattered Radiation at the Image Receptor . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.1 Air-Gap Technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.2 Slot Technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.3 Anti-scatter Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4 Quantities for the Description of the Characteristics of Grids . . . . . . . . . . . . 7.5 Derived Quantities for the Description of the Efficiency of Anti-scatter Grids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.6 Application Limits for Focused Grids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

53 53 56 56 56 58

Image Receptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1 Characteristics of Phosphor Screens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2 Digital Image Receptors and CT Receptors . . . . . . . . . . . . . . . . . . . . . . . . . 8.3 Automatic Exposure Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.1 Direct Technique (in Connection with Film-Screen Systems) . . . . . . 8.3.2 Fluoroscopy and Indirect Technique (in Connection with an Image Intensifier) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.3 Digital Imaging (Using Flat Panel Detectors) . . . . . . . . . . . . . . . . . . 8.3.4 Computed Tomography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4 Image Receptor Dose/Dose Rate (System Dose/Dose Rate) . . . . . . . . . . . . . 8.4.1 Analogue Image Receptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.2 Digital Image Receptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

67 68 70 73 73 75 76 78 78 78 81 82

Image Quality and Dose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1 Characteristics of Image Receptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2 Contrast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3 Sharpness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4 Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

85 86 87 89 92

58 58 59 59 60 62 63 65

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9.5 Signal-to-Noise Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6 Detective Quantum Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.7 Other Image-Quality Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.8 Dependence of Image Quality on Exposure Parameters . . . . . . . . . . . . . . . 9.9 Detection of Covered Structures in the X-Ray Image . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Part III

93 94 96 98 99 99

Clinical Applications

Evaluation of Dose to the Patient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1 Specific Dosimetric Quantities Used for Patient-Dose Evaluation . . . . . . . 10.2 Quantities Influencing Patient Dose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3 Initial Dosimetric Quantities for the Estimation of Organ Doses . . . . . . . . 10.4 Determination of the Initial Dosimetric Quantities . . . . . . . . . . . . . . . . . . . 10.4.1 Radiography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4.2 Fluoroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4.3 Mammography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4.4 Computed Tomography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5 Estimation of Organ Doses from the Initial Dosimetric Quantities . . . . . . . 10.5.1 Estimation of Organ Doses HT by the Use of Conversion Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5.2 Estimation of the Absorbed Dose to an Organ Dorg by the Use of Tissue-Air Ratios or Relative Depth Doses . . . . . . . 10.6 Estimation of Effective Dose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.7 Uncertainties in Patient-Dose Estimation . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

115 116 117 119

11

Scattered Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 Influence on Image Quality and Dose . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 The Various Types of Anti-scatter Grids . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2.1 Employment of Grids in Paediatrics . . . . . . . . . . . . . . . . . . . . . . . 11.2.2 Employment of Grids in Mammography . . . . . . . . . . . . . . . . . . . . 11.2.3 Employment of Grids in Digital Radiography . . . . . . . . . . . . . . . . 11.2.4 Cone-Beam Computed Tomography (CBCT) . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

121 121 123 123 125 127 129 131

12

Optimisation of Image Quality and Dose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.1 General X-Ray Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.2 Angiography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.3 Mammography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4 Computed Tomography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

133 133 134 137 142 143

10

Part IV

105 105 106 109 109 109 111 111 112 112 112

Supplement

13

X-Ray Spectra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 13.1 General X-Ray Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 13.2 Mammography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162

14

Interaction Coefficients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 14.1 Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 14.2 Compounds and Mixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

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Characteristics of the Primary Radiation Beam . . . . . . . . . . . . . . . . . . . . . . . . 199 15.1 General X-Ray Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199 15.2 Mammography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236

16

Characteristics of the Imaging Radiation Field . . . . . . . . . . . . . . . . . . . . . . . . . 257 16.1 General X-Ray Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 16.2 Mammography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283

17

Miscellaneous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.1 Penetration and Absorption of X-rays . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.2 X-ray Detectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.3 Image Quality Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

18

Patient Dose Estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 18.1 General X-Ray Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 18.2 Mammography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298

Index

285 285 286 291

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